If you want to make small plastic copies of architectural features such as decorative moulding, a vacuum form machine may be exactly what you need. This machine uses vacuum suction to mould hot sheets of plastic around a simple original form. Vacuum form machines are used on a large scale, and are so large they sometimes fill entire rooms. You can build a small version with common materials, that is powered by a shop vacuum and your kitchen oven.
- Skill level:
Things you need
- 2 pieces of 1/2-inch plywood, each 12 by 13 inches
- 2 pieces of 1/2-inch plywood, each 12 by 8 inches
- Wood screws
- Plastic sheet, 1/4-inch thick, 9 by 13 inches
- Shop vacuum
- Baking tray, 9 by 13 inches
- 1/2-inch wooden dowel
- Window screen frame kit
- Bulldog clips
- Thermoplastic sheet
- Object to be moulded
- Oven gloves
Assemble the plywood into a box that is 12 inches tall, 13 inches long and 9 inches wide. The 8-inch pieces of plywood will be sandwiched between the 13-inch pieces. Drill pilot holes in the corners to prevent the wood from splitting, then secure each corner with three 1-inch wood screws.
Cut an arch shaped like an upside-down "U" in the bottom of one of the 9-inch sides. It should be large enough to pass a shop vacuum hose through.
Cut a hole in the centre of the plastic sheet just large enough to fit the shop vacuum's nozzle into. To do this, first drill a hole large enough to get a jigsaw blade into, then cut the hole.
Pass the vacuum hose through the arch in the bottom of the box, then glue it into the hole in the plastic with epoxy. The nozzle should be flush with the surface of the plastic.
Draw a grid of 1-inch squares on the bottom of a 9-by-13-inch baking tray. Drill a 1/16-inch hole at every point where the lines intersect. The result will resemble a perforated surface similar to an air hockey table.
Drill a 1/4-inch hole every 2 inches along the lip of the baking tray.
Line up the baking tray with the plastic. Mark the holes through the baking tray's lip onto the plastic with a marker.
Drill 1/4-inch holes through the marked areas around the edge of the plastic sheet.
Glue the plastic to the box with epoxy. Drill pilot holes into the wood through the holes around the edge of the plastic.
Cut six pieces of 1/2-inch wooden dowel to match the depth of the baking tray. Spread them out onto the plastic surface and glue them in place with epoxy. These will prevent the baking tray from buckling under the vacuum pressure.
Glue the baking tray upside down to the plastic with epoxy, then screw a wood screw through each hole around the lip. The screws will pass through the corresponding holes in the plastic and into the pilot holes in the top of the box.
Allow the epoxy to dry.
Assemble two 9-by-13-inch frames using a window screen frame kit.
Tips and warnings
- To use this vacuum form machine, place an object to be moulded (such as a toy pyramid) on the perforated surface. Clamp a 9-by-13-inch sheet of thermoplastic between the two frames, using bulldog clips. Put the plastic in your oven on low heat until it begins to sag. Turn on the vacuum, which will suck air through the holes in the surface. Use oven gloves to remove the frame from the oven and press the plastic over the object onto the baking tray. The vacuum will suck the plastic down against the object. After 30 seconds, turn off the vacuum and remove the object from the plastic mould.
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